Battery pack-detecting charger

Description

FIELD OF THE INVENTION

This invention relates generally to battery chargers and more particularly to battery chargers with protection circuitry.

BACKGROUND OF THE INVENTION

The battery packs for portable power tools, outdoor tools and certain kitchen and domestic appliances may include rechargeable batteries, such as lithium, nickel cadmium, nickel metal hydride and lead-acid batteries, so that they can be recharged rather than be replaced. Thereby a substantial cost saving is achieved.

It is preferable to provide a charger that recognizes when a battery pack has been connected in order to begin charging.

SUMMARY OF THE INVENTION

In accordance with the present invention, an improved battery pack charger is employed. The charger includes a controller having an input and an output, a first terminal for connecting a battery pack to the controller, a connecting line disposed between the first terminal and the input of the controller, a current source connected to the controller for providing power to the battery pack, the current source providing the power to the battery pack via the connecting line, wherein the controller sends a pulse signal unto the connecting line via the output, whereby the controller determines whether the battery pack is connected to the charger by the presence of the pulse signal in the input of the controller.

Additional features and benefits of the present invention are described, and will be apparent from, the accompanying drawings and the detailed description below.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate preferred embodiments of the invention according to the practical application of the principles thereof, and in which:

FIG. 1 is a simplified block diagram of a battery pack and charger;

FIG. 2 is a flowchart showing a method according to the present invention;

FIG. 3 is a schematic diagram of the charger according to the present invention.

DETAILED DESCRIPTION

The invention is now described with reference to the accompanying figures, wherein like numerals designate like parts.

Referring to FIGS. 1-2, a battery pack 10 is connected to a charger 20. Battery pack 10 may comprise a plurality of battery cells 11 connected in series and/or parallel, which dictate the voltage and storage capacity for battery pack 10. Battery pack 10 may include three battery contacts: first battery contact 12, second battery contact 13, and third battery contact 14. Battery contact 12 is the B+ (positive) terminal for battery pack 10. Battery contact 14 is the B− or negative/common terminal. Battery contact 13 is the S or sensing terminal. Battery contacts 12 and 14 receive the charging current sent from the charger 20 (preferably from current source 22, as discussed below) for charging the battery pack 10.

As shown in FIG. 1, the battery cells 11 are connected between the battery contacts 12 and 14. In addition, preferably connected between battery contacts 13 and 14 is a temperature sensing device 15, such as a negative temperature co-efficient (NTC) resistor, or thermistor, R_T. The temperature sensing device is preferably in closer proximity to the cells 11 for monitoring of the battery temperature. Persons skilled in the art will recognize that other components, such as capacitors, etc., or circuits can be used to provide a signal representative of the battery temperature.

The charger 20 preferably comprises a controller 21, which in turn includes positive terminal (B+) 17 and negative (B−) terminal 18, which are coupled to battery pack 10 via battery contacts 12 and 14, respectively. The positive terminal may also act as an input, preferably an analog/digital input A/D, in order for the controller 21 to detect the battery pack voltage. In addition, the controller 21 may include another input TC, preferably an analog/digital input, which is coupled to the temperature sensing device 15 via the third battery contact 13 (S). This allows the controller 21 to monitor the battery temperature.

Controller 21 may include a microprocessor 23 for controlling the charging and monitoring operations. Controller 21 may control a charging power source for providing power to the battery pack 10, such as current source 22 that provides current to battery pack 10. This current may be a fast charging current and/or an equalization current. Current source 22 may be integrated within controller 21.

Controller 21 may have a memory 25 for storing data. Memory 25 may be integrated within controller 21 and/or microprocessor 23.

Controller 21 preferably has a pulse output PO, which sends a pulse signal unto the same line that sends power to the battery pack 10. The pulse signal may have an amplitude of 5 volts. Preferably the pulse signal generated by the controller 21 goes through a diode D23 and/or a resistor R54.

With such arrangement, controller 21 can determine whether a battery pack 10 has been connected to the charger 20. FIG. 2 is a flowchart illustrating the process for determining whether a battery pack 10 has been connected to the charger 20.

First, the current source 22 must be off (ST1). The controller 21 then sends a pulse signal via pulse output PO (ST2).

The controller 21 then checks whether the input A/D has received a pulse (ST3). If a pulse was received, a battery pack 10 is not connected to the charger 20.

On the other hand, if a pulse was not received, the controller 21 would interpret this to mean that a battery pack 10 is connected to the charger 20. Persons skilled in the art will recognize that the voltage at input A/D will be substantially constant since resistor R54 and diode D23 will not allow a significant current to generate an AC signal across the battery. Since the pulse was not received, controller 21 would then start charging battery pack 10 by turning on current source 22 (ST4).

Controller 21 then senses the battery voltage V0 via input A/D (ST5). Controller 21 compares battery voltage V0 to a certain threshold X (ST6). If battery voltage V0 is below threshold X, charging continues and controller 21 continues to sense and compare the battery voltage V0.

If battery voltage V0 exceeds (or is equal to) threshold X, controller 21 then assumes that the battery pack 10 has been removed from charger 20 and stops charging by turning the current source off. Persons skilled in the art will recognize that it is preferable to provide a relatively high threshold so as to not prematurely terminate charging, resulting in an undercharged battery pack. Accordingly, it is preferable to provide a threshold of at least 30 volts.

FIG. 3 is an exemplary schematic diagram of the charger of FIG. 1. Preferably, the values of the different components of are as follows:

C1	0.1 microfarads
C2A	1,000 microfarads
C2B	1,000 microfarads
C2C	1,000 microfarads
C3	0.1 microfarads
C5	102 picofarads
C6	0.1 microfarads
C7	47 microfarads
C8	0.001 microfarads
C9	0.1 microfarads
C10	0.001 microfarads
C11	220 picofarads
C12	0.1 microfarads
C14	0.01 microfarads
C15	0.1 microfarads
C22	1 microfarads
C26	1 microfarads
C29	0.1 microfarads
C51	0.1 microfarads
C52	0.01 microfarads
C62	100 picofarads
C65	0.001 microfarads
C67	0.01 microfarads
C68	0.1 microfarads
C69	47 microfarads
C70	0.0022 microfarads
C71	0.22 microfarads
C72	0.1 microfarads
CR51	Diode FRD T220 STPR1020CT
D2	Diode FRD 1 A 1000 V DO204 BYV26E
D6	Diode SW .3 A 75 V MELF
D7	Diode SW 200 mA 75 V DO-35
D8	Diode SW .3 A 75 V MELF
D9	Diode SW 200 mA 75 V DO-35
D10	Diode SW .3 A 75 V MELF
D11	Diode SW .3 A 75 V MELF
D17	Diode SW .3 A 75 V MELF
D21	Diode SW .3 A 75 V MELF
D22	Diode SW .3 A 75 V MELF
D23	Diode SW 200 mA 75 V DO-35
D29	Diode SW .3 A 75 V MELF
FL1	LF 780 microhenries
IC1	UC3845BN
IC2	Microprocessor
IC4	LM358
L1	1.1 microhenries
L2	1.1 microhenries
NTC1	thermistor, 100K
Q1	FET 60 V 50 A T220 IRFZ44N
Q2	FET 60 V 50 A T220 IRFZ44N
Q3	MMBT4401 SMT
Q7	MMBT4403 SMT
Q8	MMBT4401 SMT
Q9	MMBT4401 SMT
R2	47 kiloohms
R4	5.1 kiloohms
R5	3 kiloohms
R6	1 kiloohms
R7	33 ohms
R8	33 ohms
R9	1 kiloohms
R10	43 kiloohms
R11	12 kiloohms
R12	220 kiloohms
R13	100 ohms
R14	18 kiloohms
R15	2.2 ohms
R16	220 kiloohms
R27	80.6 kiloohms
R28	14 kiloohms
R31	47.5 kiloohms
R33	39 kiloohms
R43	470 ohms
R47	8.25 kiloohms
R48	8.2 kiloohms
R49	10 kiloohms
R52	1 kiloohms
R53	4.02 kiloohms
R54	470 ohms
R55	4.7 kiloohms
R56	82 kiloohms
R57	2 kiloohms
R58	1 kiloohms
R59	10 kiloohms
R60	82 kiloohms
R61	100 kiloohms
R62	100 kiloohms
R63	100 kiloohms
R64	470 ohms
R66	10 kiloohms
R67	100 kiloohms
R68	1 kiloohms
R69	10 kiloohms
R76	100 kiloohms
R83	100 kiloohms
R86	910 ohms
R87	1 kiloohms
R94	330 ohms
R95	1.2 kiloohms
R96	1.5 kiloohms
R97	1.2 kiloohms
R98	30 kiloohms
R99	200 kiloohms
R100	10 kiloohms
R101	10 kiloohms
R102	300 ohms
R103	10 kiloohms
T1	Transformer
U4	Voltage Regulator IC 5 V 0.1 A T92 3PIN 7805
VR51	Variable Resistor 1 kiloohms
Z1	Varistor 20 VAC 6 J 1000 A
ZD1	Zener Diode 0.5 W 18 B MELF
ZD2	Zener Diode 0.5 W 20 B MELF
ZD3	Zener Diode 0.5 W 6.2 B MELF
ZD4	Zener Diode P6KE51A
ZD5	Zener Diode 0.5 W 15 B MELF
ZD6	Zener Diode 0.5 W 15 B DO-35
ZD7	Zener Diode 0.5 W 5.1 C MELF
ZD8	Zener Diode 0.5 W 5.1 C MELF
ZD9	Zener Diode 0.5 W 12 C MELF
ZD51	Zener Diode 0.5 W 36 V RLZTE1139B/TZMB36 MELF

Persons skilled in the art will recognize that the pulse output PO and input are pins 15 and 7 of IC2, respectively. Persons skilled in the art will also recognize that diode D23 and resistor R54 are the same components in FIGS. 1 and 3.

Persons skilled in the art should recognize that the charger shown in FIG. 3 is connectable to a vehicle battery, rather than to an AC source. Nevertheless, persons skilled in the art will know how to modify the power supply within the charger to accept power from an AC source.

Finally, persons skilled in the art may recognize other additions or alternatives to the means disclosed herein. However, all these additions and/or alterations are considered to be equivalents of the present invention.